Pursuant to Federal Motor Vehicle Safety Standard (FMVSS) 114, all automobiles with automatic transmissions must incorporate a mechanism for preventing the automobile from moving when set to “park.” Similar standards apply to other types of vehicles. The most common solution utilized in North America is a park pawl mechanism. A park pawl is a thick metal component having a single tooth feature. When an automobile is set to “park,” the park pawl tilts and the single tooth feature is locked into a corresponding gear, typically referred to as the output gear or pawl gear, thereby preventing the automobile from moving.
Such park pawl mechanisms are, unfortunately, prone to error. Most park pawls utilize a spring-loaded piston that applies pressure to the park pawl when the automobile is set to “park.” Monitoring is performed upstream of the spring, thereby monitoring only actuation of the park pawl linkage, and not actual engagement of the park pawl with the output gear. If actual engagement of the park pawl is monitored, it is done by sensing the rotation of the output gear itself—after the park pawl has already failed and potentially dangerous automobile motion has already occurred. This is usually accomplished by monitoring the mechanical linkages associated with the park pawl or using speed sensors. The safety of the automobile is therefore compromised.
Thus, what is still needed in the art is an improved park pawl mechanism that ensures both the actuation of the park pawl linkage and actual engagement of the park pawl with the output gear, thereby enhancing the safety of the automobile.